Subcutaneous and intramuscular delivery of liquid drugs by injection is common in the medical arts. As some medications such as insulin must be given frequently by injection to an individual, easy performance of the injections is desirable.
Some patients dislike needle injections due to pain or fear for needles. Further, blood-borne pathogens, such as HIV and hepatitis, can be transmitted to health care workers by accidental needle-sticks. Also, the disposal of used needles is a growing concern. This disposal presents a problem to individuals other than healthcare workers. Children, for example, may find used needles in the garbage, putting them at risk of contracting infection. Discarded needles likewise pose a risk to waste disposal workers.
In efforts to minimize the fears and risks associated with needle injections, several types of needle-free jet injectors have been developed. These devices penetrate the skin using a high velocity fluid jet and deliver medication into the tissue of a patient. In order to accomplish this, a force is exerted on the liquid medication. Jet injectors in general contain a fluid drug which has been transferred into a chamber having a small orifice at one end. The high velocity fluid jet can be achieved for instance by having a drive means, e.g. a ram, accelerated using either a coil spring or a compressed gas energy source. The ram impacts a plunger which in turn creates a high pressure impulse within the chamber. This pressure impulse ejects the fluid medicament through the orifice at high velocity, piercing the skin. The energy source continues to apply a force to the plunger which quickly propels the drug through the opening in the skin, emptying the syringe in a fraction of a second.
The nozzle orifice of a prefilled drug cartridge for a jet injection device requires to be sealed by a protective system to ensure closure integrity of the drug reservoir since it constitutes a primary packaging during storage. The reservoir containing the drug is defined by an inside cavity of the cartridge, and is delimited by the inside cartridge nozzle walls, the plunger in the proximal end of the cartridge sealed towards the cartridge walls, and the distal end of the cartridge penetrated by a nozzle orifice. The orifice opening is the area which poses the highest risk of impurification, spilling or contamination of the drug, since it gives direct access from the environment to the drug contained in the reservoir. Therefore it is of vital importance that a safe and reliant seal of the nozzle orifice is provided.
The nozzle quality is crucial for the system to provide a jet able to penetrate the skin and deliver to the target area of the tissue which is often the subcutis but also other areas. This means that at the time of extrusion of a drug, the nozzle geometry must be unaltered and the nozzle must be clear from any residues from the sealing elements. Therefore any sealing of the nozzle must be removable in a manner that allows reestablishment of the nozzle quality. This poses certain requirements on the protective system.
Also there is a need for a tamper proof feature that clearly signals to the user whether the content of the injection device has been properly protected during storage.
Good performance of jet injection systems can among others be obtained by fixation of the nozzle to the skin to be penetrated. Among the options to do this are vacuum or adhesives where the tip of the cartridge has an adhesive enabled fixation to the skin during injection. In case of an adhesive system, a protective system could be a foil, for instance an alu foil fixed by the skin adhesive. However this can not in all cases be expected to give sufficient aseptic closure integrity due to the relative weak adhesive forces of such a skin fixation system. In these cases a more distinct system is required.
Addressing this problem, U.S. Pat. No. 4,010,747 disclose a needleless injector having at the injection nozzle end a closure member covering the injection opening and the surrounding area. The closure member may be formed of plastic, a wax layer or a varnish layer provided with an adhesive backing. When the closure member is removed, the injection opening is exposed. U.S. Pat. No. 4,010,747 suffers from the mentioned drawback that the sealing system is not sufficiently distinct to give reliable protection of the nozzle area, as the closure member is a relatively crude seal, not specifically designed to locally protect the injection opening. Of course, since the injector is not intended to be prefilled, such a well defined and secure closure integrity is not equally important as it is in one of the embodiments of the present invention. DE 10155344 also describes a closure member for a needleless injector, the closure member being more distinct as it comprises a plug which locally closes the injection opening. The plug is the central member of a closure cap connected to the nozzle area of the injector by a thread-connection. This closure has the disadvantage, that it gives no evidence as to whether the sealing has been tampered or not. There is a risk that the closure could have been dis- and re-mounted prior to use thereby exposing the nozzle area for damage or foreign bodies and potential contaminant of a drug contained in the device. Also, even though the central closure member of DE 10155344 is more distinct, sufficient closure integrity is not ensured, since the sealing is sensitive to the applied closure force of the thread-connection, a parameter difficult to control.
Examples of cap closures for needleless injectors are described in GB 705516, WO 03015853, EP 0595508 and U.S. Pat. No. 6,409,032 (which concerns a break-off closure member for a needleless injector), all of them however lacking a distinct closure of the area local to the injection opening.
In view of the above, one of the objectives of the present invention is to provide a sealing membrane for a medical jet injection device which ensures a safe, well defined distinct closure of the nozzle area local to the injection opening of the device, to acquire protection of the nozzle orifice and contamination repelling storage of a drug contained in the device. A further objective of the invention is to provide a sealing membrane combining the aforementioned objectives with a tamper evident solution, providing user reassurance. Furthermore, an objective of the present invention is to provide a sealing membrane which is simple and easy to use, small and manufactured cost-effectively. It is also an objective to provide a sealing membrane applicable to conventional jet injection devices, contributing to the comfort of the patient, so that the jet injection device can easily be utilized by a non-professional user, e.g. an insulin dependant diabetic.